Paraffinic hydrocarbon isomerization process

ABSTRACT

Isomerizable hydrocarbons including paraffins, cycloparaffins, olefins and alkyl aromatics are isomerized by contacting the hydrocarbon at isomerization conditions with a catalytic composite comprising a platinum group metal on an alpha-alumina monohydrate support wherein said support is prepared by admixing an alpha-alumina monohydrate with an aqueous ammoniacal solution having a pH of at least about 7.5 to form a stable suspension and commingling said suspension with a salt of a strong acid to form an extrudable paste or dough. Upon extrusion, the extrudate is dried and calcined to form said alumina support.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of copending application Ser.No. 788,376 filed Apr. 18, 1977 and now U.S. Pat. No. 4,098,874 whichissued on July 4, 1978. The teachings of which application areincorporated herein by reference thereto.

BACKGROUND OF THE INVENTION

This invention relates to a process for isomerizing isomerizablehydrocarbons, and in particular, isomerizable paraffins, cycloparaffins,olefins and alkylaromatic. More particularly, this invention relates toa process for isomerizing isomerizable hydrocarbons with a catalyticcomposite comprising a combination of a platinum group metal component,and an alpha-alumina monohydrate support wherein said support isprepared by admixing a finely divided alpha-alumina monohydrate with anaqueous ammoniacal solution having a pH of at least about 7.5 andforming a stable suspension, commingling a metal salt of a strong acidwith said suspension and converting the suspension to an extrudablepaste or dough, extruding the paste or dough, drying and calcining theextruded alumina.

Isomerization processes for the isomerization of hydrocarbons haveacquired significant importance within the petrochemical and petroleumrefining industry. The demand for the xylene isomers, particularlypara-xylene, has resulted in the need for processes for isomerizingxylenes and ethylbenzene to obtain a desired xylene isomer such aspara-xylene. Also, the need for branched chain paraffins such asisobutane or isopentane as intermediates for the production of highoctance motor fuel produced by alkylation, it is desired that the finalalkylate be highly branched. This can be accomplished by alkylatingisobutane or isopentane with a C₄ -C₇ internal olefin which, in turn,can be produced by the isomerization of the linear alphaolefin byshifting the double bond to a more central position.

SUMMARY OF THE INVENTION

Accordingly, it is an object of this invention to provide a process forisomerizing isomerizable hydrocarbons. More specifically, it is anobject of this invention to provide an isomerization process using aparticular isomerization catalyst effective in isomerizing isomerizablehydrocarbons without introducing undesired decomposition reactions.

In a broad embodiment, this invention relates to a process forisomerizing an isomerizable hydrocarbon which comprises contacting saidhydrocarbon with a catalytic composite comprising a combination of aplatinum group metal component, and an alumina support wherein saidsupport is prepared by admixing a finely divided alpha-aluminamonohydrate with an aqueous ammoniacal solution having a pH of at leastabout 7.5 and forming a stable suspension, commingling a metal salt of astrong acid with said suspension and converting the suspension to anextrudable paste or dough, extruding the paste or dough, drying andcalcining the extruded alumina.

In a more specific embodiment, this invention relates to theisomerization of either a saturated or olefinic isomerizable hydrocarbonby contacting the hydrocarbon with the aforementioned catalyticcomposite at isomerization conditions which include a temperature ofabout 0° C. to about 425° C., a pressure of about atmospheric to about100 atmospheres, and a liquid hourly space velocity of about 0.1 toabout 20.0 hr.⁻¹. In another limited embodiment, this process relates tothe isomerization of an isomerizable alkylaromatic hydrocarbon bycontacting an alkylaromatic with the aforementioned catalytic compositeat isomerization conditions which include a temperature of about 0° C.to about 600° C., a pressure of about atmospheric to about 100atmospheres, a liquid hourly space velocity of about 0.1 to about 20.0hr.⁻¹ and a hydrogen to hydrocarbon mole ratio of about 0.5:1 to about20:1.

In a more specific embodiment, the catalytic composite used inisomerizing the foregoing isomerizable hydrocarbons contains, on anelemental basis 0.1 to about 5 weight percent halogen and about 0.1 toabout 2 weight percent platinum group metal.

In another embodiment, this invention relates to a catalytic compositewhich comprises alumina, having combined therewith platinum groupmetallic component and a Friedel-Crafts metal halide component.

Other objects and embodiments referring to alternative isomerizablehydrocarbons and to alternative catalytic compositions will be found inthe following further detailed description of this invention.

DETAILED DESCRIPTION

The process of this invention is applicable to the isomerization ofisomerizable saturated hydrocarbons including acyclic paraffins andcyclic naphthenes and is particularly suitable for the isomerization ofstraight chain or mildly branched chain paraffins containing 4 or morecarbon atoms per molecule such as normal butane, normal pentane, normalhexane, normal heptane, normal octane, etc., and mixtures thereof.Cycloparaffins applicable are those ordinarily containing at least 5carbon atoms in the ring such as alkylcyclopentanes and cyclohexanes,including methylcyclopentane, dimethylcyclopentane, cyclohexane,methylcyclohexane, dimethylcyclohexane, etc. This process also appliesto the conversion of mixtures of paraffins and/or naphthenes such asthose derived by selective fractionation and distillation ofstraight-run natural gasolines and naphthas. Such mixtures of paraffinsand/or naphthenes include the so-called pentane fractions, hexanefractions, and mixtures thereof. It is not intended to limit thisinvention to these enumerated saturated hydrocarbons, and it iscontemplated that straight or branched chain saturated hydrocarboncontaining up to about 20 carbon atoms per molecule may be isomerizedaccording to the process of the present invention with C₄ -C₇ n-alkanesbeing particularly preferred.

The olefins applicable within this isomerization process are generally amixture of olefinic hydrocarbons of approximately the same molecularweight, including the 1-isomer, 2-isomer, and other position isomers,capable of undergoing isomerization to an olefin in which the doublebond occupies a more centrally located position in the hydrocarbonchain. The process of this invention can be used to provide an olefinicfeed stock for motor fuel alkylation purposes containing an optimumamount of the more centrally located double bond isomers, by convertingthe 1-isomer, or other near terminal position isomer into olefinswherein the double bond is more centrally located in the carbon atomschain. The process of this invention is also applicable to theisomerization of such isomerizable olefinic hydrocarbons such as theisomerization of 1-butene to 2-butene or the isomerization of the3-methyl-1-butene to 2-methyl-2-butene. Also, the process of thisinvention can be utilized to shift the double bond of an olefinichydrocarbon such as 1-pentene, 1-hexene, 2-hexene, and4-methyl-1-pentene to a more centrally located position so that2-pentene, 2-hexene, 3-hexene and 4-methyl-2-pentene, respectively, canbe obtained. It is not intended to limit this invention to theseenumerated olefinic hydrocarbons as it is contemplated that shifting ofthe double bond to a more centrally located position may be effective instraight or branched chain olefinic hydrocarbons containing up to about20 carbon atoms per molecule. Preferred are linear C₄ -C₇alpha-mono-olefins. The process of this invention also applies to thehydroisomerization of olefins wherein olefins are converted tobranched-chain paraffins.

Further, the process of this invention is also applicable to theisomerization of isomerizable alkylaromatic hydrocarbons includingortho-xylene, meta-xylene, para-xylene, ethylbenzene, the ethyltoluenes,the trimethylbenzenes, the diethylbenzenes, the triethylbenzenes, normalpropylbenzene, isopropylbenzene, etc., and mixtures thereof. Preferredisomerizable alkylaromatic hydrocarbons are the monocyclic alkylaromatichydrocarbons, that is, the alkyl benzene hydrocarbons, particularly theC₈ alkylbenzenes, and nonequilibrium mixtures of the various C₈ aromaticisomers.

These foregoing isomerizable hydrocarbons may be derived as selectivefractions from various naturally-occurring petroleum streams either asindividual components or as certain boiling range fractions obtained bythe selective fractionation and distillation of catalytically crackedgas oil. Thus, the process of this invention may be successfully appliedto and utilized for complete conversion of isomerizable hydrocarbonswhen these isomerizable hydrocarbons are present in minor quantities invarious fluid or gaseous streams. Thus, the isomerizable hydrocarbonsfor use in the process of this invention need not be concentrated. Forexample, isomerizable hydrocarbons appear in minor quantities in variousrefinery streams, usually diluted with gases such as hydrogen, nitrogen,methane, ethane, propane, etc. These refinery streams containing minorquantities of isomerizable hydrocarbons are obtained in petroleumrefineries and various refinery installation including thermal crackingunits, catalytic cracking units, thermal reforming units, coking units,polymerization units, dehydrogenation units, etc. Such refineryoffstreams have in the past often been burned for fuel value, since aneconomical process for the utilization of the hydrocarbon content hasnot been available. This is particularly true for refinery fluid streamsknown as off gas streams containing minor quantities of isomerizablehydrocarbons.

As indicated in the embodiments, the catalyst utilized in the presentisomerization process comprises a platinum group metal component, and ahalogen component incorporated on alpha-alumina monohydrate supportmaterial.

The alpha-alumina monohydrate employed herein is preferably analpha-alumina monohydrate derived from the water hydrolysis of analuminum alkoxide. More preferably, the alpha-alumina monohydrate is aproduct of the well-known Ziegler process. The alpha-alumina monohydrateis thus preferably prepared stepwise starting with the reaction ofaluminum, hydrogen and ethylene. After a further polymerization stepwith ethylene, the trialkyl aluminum polymerization product is oxidizedto form an aluminum alkoxide which, on subsequent water hydrolysis,yields an alumina slurry and an alcohol product. The alumina recoveredfrom the reaction mixture is generally treated for the removal ofresidual alcohols, for example by solvent extraction, and/or steamstripping, and then dried to produce the alpha-alumina monohydrate in afinely divided state.

Pursuant to the present invention, the finely divided alpha-aluminamonohydrate is admixed with an aqueous alkaline solution having a pH ofat least about 7.5, and preferably from about 7.5 to about 8.5. Thealpha-alumina monohydrate added to the stirred aqueous alkaline solutionforms a stable suspension having the consistency of a light whippedcream--the suspension being Newtonian in character with little if anythixotropic or dilatant behavior.

The alumina is preferably admixed with a sufficient amount of aqueoussolution to provide an extrudable paste or dough comprising from about30 to about 60 wt. % alumina. The aqueous alkaline solution ispreferably an aqueous ammoniacal solution. Suitable ammoniacal solutionsinclude solutions of bases such as ammonium hydroxide, hydroxylamine,hydrazine, tetramethylammonium hydroxide, etc., or a strong organicamine like methylamine, dimethylamine, ethylamine, diethylamine,propylamine, diisopropylamine, n-butylamine, t-butylamine,diisobutylamine, n-amylamine, n-hexylamine, ethylenediamine,hexamethylenediamine, benzylamine, aniline, piperizine, piperadine, andthe like, the selected base being employed in sufficient concentrationto provide a pH of at least about 7.5, and preferably from about 7.5 toabout 8.5.

With the addition of a metal salt of a strong acid to the stirredsuspension as herein contemplated, the suspension becomes very fluid fora brief period permitting the suspension to become thoroughly anduniformly mixed before setting to a firm extrudable paste. The selectedmetal salt is conveniently an aluminum salt whereby the aluminumprovides a portion of the alumina of the finished product. However, themetal salt may comprise one or more metals exhibiting a catalytic effectwith respect to one or more hydrocarbon conversion reactions wherebysaid metal or metals appear as a catalytic component of the finalalumina product. The metal salt is suitably added to the stirredsuspension as an aqueous solution thereof in an amount to providesufficient acid anions to convert said suspension to an extrudablepaste, an amount which is usually equivalent to that required to providefrom about 1 to about 10 wt. % of the metal content of the finishedproduct. Suitable metal salts of a strong acid particularly include thenitrates, sulfates and halides, and especially the nitrates, forexample, aluminum nitrate, ferric nitrate, nickel nitrate, cobaltnitrate, chromium nitrate, copper nitrate, palladium nitrate, silvernitrate, zinc nitrate, stannous and stannic nitrate and the like.

Extrusion of the paste or dough can be effected in accordance with priorart practice. Thus, utilizing a conventional screw type extruder, thedough or paste is processed through a die plate generally comprisingorifice openings in the 1/32-1/4 inch diameter range. The freshlyextruded material may be collected in the form of strands of indefiniteor random lengths to be dried and subsequently broken into extrudateparticles; or the freshly extruded material may be cut into random orpredetermined lengths and subsequently dried; or the freshly extrudedmaterial may be formed into spheres, for example, by the process wherebythe extrudate strands are collected in a spinning drum--the strandsbecoming segmented and spheroidized under the spinning influence of thedrum.

In any case, the extrudate is dried and subsequently calcined. Suitabledrying is accomplished at a temperature of from about 100° to about 120°C. in an air atmosphere using a forced draft oven. The extrudate productcan be dried and calcined at a temperature of from about 450° to about850°, but preferably at a temperature of from about 550° to about 750°C. in a flow of air containing 1 to 5 wt. % steam to produce a calcinedproduct having a surface area of from about 165 to about 215 m² /g and apore volume of from about 0.3 to about 0.4 cc/g and the pore diameterrange of from about 20 to about 80 Angstroms.

An essential constituent of the catalyst of the present invention is ahalogen component. Although the precise form of the chemistry of theassociation of the halogen component with the alumina support is notentirely known, it is customary in the art to refer to the halogencomponent as being combined with the alumina support, or with the otheringredients of the catalyst. This combined halogen may be eitherfluorine, chlorine, iodine, bromine, or mixtures thereof. Of these,fluorine and particularly, chlorine are preferred for the purposes ofthe present invention. In addition, fluorine and chlorine may beutilized together. The halogen may be added to the alumina support inany suitable manner, either during preparation of the support or beforeor after the addition of the catalytically active metallic components.For example, the halogen may be added, at any stage of the preparationof the support or to the calcined support, as an aqueous solution of anacid such as hydrogen fluoride, hydrogen chloride, hydrogen bromide,etc., or as an acid salt such as ammonium bifluoride, etc. The halogencomponent or a portion thereof, may be composited with alumina duringthe impregnation of the latter with the platinum group component; forexample, through the utilization of a mixture of chloroplatinic acid andhydrogen chloride. In any event, the halogen will be typicallycomposited with the alumina support in such a manner as to result in afinal composite that contains on an elemental basis, about 0.1 percentto about 5 percent and preferably about 0.4 to about 1 percent by weightof chlorine when chlorine is used as the halogen or about 0.5 to about3.5 percent by weight when fluorine is utilized.

As indicated above, the catalyst of the present invention also containsa platinum group metallic component. Although the process of the presentinvention is specifically directed to the use of a catalytic compositecontaining platinum, it is intended to include other platinum groupmetals such as palladium, rhodium, ruthenium, etc. Preferred isplatinum, palladium and compounds thereof. The platinum group metalliccomponent, such as platinum, may exist within the final catalyticcomposite as a compound such as an oxide, sulfide, halide, etc., or asan elemental state. Generally, the amount of the platinum group metalliccomponent present in the final catalyst is small compared to thequantities of the other components combined therewith. In fact, theplatinum group metallic component generally comprises about 0.01 toabout 1 percent weight of the final catalytic composite calculated on anelemental basis. Excellent results are obtained when the catalystcontains about 0.3 to about 0.9 wt. percent of the platinum group metal.

The platinum group metal component is suitably composited with thesupport or carrier material by impregnation and/or ion-exchangetechniques familiar to the art. For example, a soluble platinum groupcompound, that is, a soluble compound of platinum, palladium, rhodium,ruthenium, osmium and/or iridium, is prepared in aqueous solution, andthe alumina particles soaked, dipped, or otherwise immersed therein.Suitable platinum group compounds include platinum chloride,chloroplatinic acid, ammonium chloroplatinate, dinitrodiaminoplatinum,palladium chloride, and the like. It is common practice to impregnatethe support or carrier material with an aqueous chloroplatinic acidsolution acidified with hydrochloric acid to facilitate an evendistribution of platinum on the support or carrier material. The supportor carrier material is preferably maintained in contact with theimpregnating solution at ambient temperature conditions, suitably for atleast about 30 minutes, and the impregnating solution thereafterevaporated to dryness. For example, a volume of the particulate supportor carrier material is immersed in a substantially equal volume ofimpregnating solution in a steam jacketed rotary dryer and tumbledtherein for a brief period at about room temperature. Steam isthereafter applied to the dryer jacket to expedite evaporation of theimpregnating solution and recovery of substantially dry impregnatedparticles. Thus, a further embodiment of this invention relates to analumina support or carrier material characterized by a surface area offrom about 165 to about 215 m² /g and a pore volume of from about 0.3 toabout 0.4 cc/g in the pore diameter range of from about 20 to about 80Angstroms, said alumina being impregnated with from about 0.1 to about 2wt. % platinum.

The alumina composition of this invention is useful as a support orcarrier material for a platinum group metal component alone or incombination with a tin component, a rhenium component, and/or agermanium component. The tin, rhenium, and/or germanium components maybe composited with the support or carrier material in any conventionalor otherwise convenient manner. Suitable methods include impregnationand/or ion-exchange of the support or carrier material with a suitablecompound of one or more of said components in any desired sequence, withor without intermediate calcination. In the impregnation of the supportor carrier material, it is a preferred practice to impregnate one ormore of said components on said support or carrier materialsimultaneously with the platinum group metal component from a commonimpregnating solution. For example, when the added component is tin,stannic chloride is conveniently and advantageously prepared in commonsolution with chloroplatinic acid, the concentration of each componenttherein being sufficient to yield a catalyst product containing fromabout 0.01 to about 2 weight percent platinum and from about 0.1 toabout 5 weight percent tin calculated as the elemental metal. Similarly,when the desired added component is rhenium, perrhenic acid andchloroplatinic acid can be prepared in a common aqueous solution toimpregnate the support or carrier material, suitably with from about0.01 to about 2 weight percent platinum and from about 0.01 to about 2weight percent rhenium. Thus, another embodiment of this inventionconcerns an alumina support or carrier material characterized by asurface area of from about 165 to about 215 m² /g and a pore volume offrom about 0.3 to about 0.4 cc/g in the pore diameter range from about20 to about 80 Angstroms, said alumina being impregnated with from about0.01 to about 2 wt. % platinum and from about 0.01 to about 2 wt. %rhenium.

The tin, rhenium, and/or germanium components and particularly the tin,and germanium components are advantageously composited with the aluminaby including a suitable acid salt thereof in the aforementionedsuspension prepared by admixing a finely divided alpha-aluminamonohydrate with an aqueous alkaline solution. For example, an acid saltof tin such as stannous or stannic chloride, may be admixed with saidsuspension and serve not only as a precursor of the desired tincomponent, but also as the metal salt of a strong acid as hereincontemplated. Following the extrusion process and subsequentcalcination, the alumina is obtained comprising the tin component inintimate combination therewith and suitable for further impregnationand/or ion exchange to incorporate, for example, the platinum groupmetal component.

Although not essential, the resulting catalytic composite can beimpregnated with an anhydrous Friedel-Crafts type metal halide,particularly aluminum chloride. Other suitable metal halides arealuminum bromide, ferric chloride, ferric bromide, zinc chloride,beryllium chloride, etc. This impregnation can be accomplished by thesublimination of the aluminum chloride onto the platinum aluminacomposite under conditions such that the sublimed aluminum chloride ischemically combined with the hydroxyl groups of the composite. Thisreaction is accompanied by the elimination of from about 0.5 to about2.0 moles of hydrogen chloride per mole of aluminum chloride reacted.Since aluminum chloride sublimes at about 184° C. suitable impregnationtemperatures range from about 190° C. to about 700° C.; preferably, 200°C. to about 600° C. The sublimation can be conducted at atmosphericpressure or under increased pressures and in the presence of diluentssuch as inert gases, hydrogen and light paraffinic hydrocarbons. Theimpregnation may be conducted batchwise but a preferred method is topass sublimed AlCl₃ vapors in admixture with an inert gas such as H₂through the calcined catalyst bed. This method both continuouslydeposits the AlCl₃ and removes the evolved HCl.

The amount of metal halide combined with the catalytic composite mayrange from about 5 to about 100 weight percent of the originalcomposite. The final composite has unreacted metal halide removed bytreating the composite at a temperature above 300° C. for a timesufficient to remove therefrom any unreacted metal halide. For aluminumchloride, temperatures of about 400° C. to about 600° C. and times offrom about 1 to about 48 hours are satisfactory. The reaction of thealuminum chloride with the hydroxyl groups of the alumina compositeyields -- Al--O--AlCl₂ active centers which can enhance the performancecharacteristics of the original catalytic composite, particularly for C₄-C₇ n-alkanes.

In addition, the resulting reduced catalytic composite may in some casesbe beneficially subjected to a presulfiding operation designed toincorporate in the catalytic composite from about 0.05 to about 5 weightpercent sulfur calculated on an elemental basis. Preferably, thispresulfiding treatment takes place in the presence of hydrogen and asuitable sulfur-containing compound such as hydrogen sulfide, lowermolecular weight mercaptans, organic sulfides, etc. Typically, thisprocedure comprises treating the reduced catalyst with a sulfiding gassuch as a mixture of hydrogen and hydrogen sulfide having about 10 molesof hydrogen per mole of hydrogen sulfide at conditions sufficient toeffect the desired incorporation of sulfur, generally including atemperature ranging from about 50° F. up to about 1100° F. or more.

According to the present invention, the isomerizable hydrocarbon, inadmixture with hydrogen, is contacted with a catalyst of the typedescribed above in a hydrocarbon conversion zone. This contacting may beaccomplished by using the catalyst in a fixed bed system, a moving bedsystem, a fluidized bed system, or in a batch type operation; however,in view of the danger of attrition losses of the valuable catalyst andof well known operational advantages, it is preferred to use a fixed bedsystem. In this system a hydrogen-rich gas and the charge stock arepreheated by any suitable heating means to the desired reactiontemperature and then are passed into a conversion zone containing afixed bed of the catalyst type previously characterized. It is, ofcourse, understood that the conversion zone may be one or more separatereactors with suitable means therebetween to insure that the desiredconversion temperature is maintained at the entrance to each reactor. Itis also to be noted that the reactants may be contacted with thecatalyst bed in either upward, downward, or radial flow fashion. Inaddition, it is to be noted that the reactants may be in the liquidphase, a mixed liquid-vapor phase, or a vapor phase when they contactthe catalyst, with best results obtained in the vapor phase.

The process of this invention, utilizing the catalyst hereinbefore setforth, for isomerizing isomerizable olefinic or saturated hydrocarbonsis preferably effected in a continuous flow, fixed bed system. Oneparticular method is continuously passing the hydrocarbon to a reactionzone containing the catalyst and maintaining the zone at properisomerization conditions such as a temperature in the range of about 0°to about 425° C. or more, and a pressure of about atmospheric to about200 atmospheres or more. The hydrocarbon is passed over the catalyst ata liquid hourly space velocity (defined as volume of liquid hydrocarbonpassed per hour per volume of catalyst) of from about 0.1 to about 20hr.⁻¹ or more. In addition, diluents such as argon, nitrogen, orhydrogen may be present. In fact, the presence of hydrogen at a hydrogento hydrocarbon mole ratio of about 0.1:1 to about 10:1 is preferred. Theisomerized product is continuously withdrawn, separated from the reactoreffluent, and recovered by conventional means, preferably fractionaldistillation, while the unreacted starting material may be recycled toform a portion of the feed stock.

Likewise, the process of this invention for isomerizing an isomerizablealkylaromatic hydrocarbon is also preferably effected by passing thearomatic to a reaction zone containing the hereinbefore describedcatalyst and maintaining the zone at proper alkylaromatic isomerizationconditions such as a temperature in the range of about 0° C. to about600° C. or more, and a pressure of atmospheric to about 100 atmospheresor more. The hydrocarbon is passed, in admixture with hydrogen, at aliquid hourly hydrocarbon space velocity of about 0.1 to about 20 hr.⁻¹or more and a hydrogen to hydrocarbon mole ratio of about 0.5:1 to about20:1. Other inert diluents such as nitrogen, argon, etc. may also bepresent. The isomerized product is continually withdrawn, separated fromthe reactor effluent by conventional means such as fractionaldistillation or crystallization, and recovered.

EXAMPLES

The following examples are given to illustrate the preparation of thecatalyst composite to be utilized in the process of this invention andits use in the isomerization of isomerizable hydrocarbons. However,these examples are not presented for purposes of limiting the scope ofthe invention but in order to further illustrate the embodiment of thepresent process.

EXAMPLE I

In this example, representative of one preferred embodiment of thisinvention, 4000 grams of a finely divided alpha-alumina monohydrate(Catapal SB alumina) was added to a rapidly stirred aqueous alkalinesolution having a pH of about 7.5. The alumina contained about 25 wt. %volatile matter, and the alkaline solution consisted of 12.9 cc ofconcentrated ammonium hydroxide diluted to 3450 cc of water. Theresulting slurry was a stable suspension having a light creamyconsistency. The suspension was Newtonian in character and gave noindication of thixotropic or dilatant behavior. After about 30 minutesof continuous stirring, an aluminum nitrate solution was added, thesolution consisting of 595 grams of Al(NO₃)₃ 9H₂ O dissolved in 1400 ccof water. The stirred suspension became very thin and extremely fluidfor about 10 seconds and thereafter set to a thick paste with a solidscontent of about 33 wt. %. The paste was subsequently extruded, ovendried for about 12 hours at 110° C., and calcined for about 2 hours at650° C. in air containing about 3 wt. % steam. The dried and calcinedalumina product had a surface area of 217 m² /g, and a pore volume ofabout 0.35 cc/g in the 40-60 Angstrom diameter range.

About 250 cc of the alumina particles were immersed in 250 cc of animpregnating solution. The impregnating solution was prepared byadmixing 46.9 cc of chloroplatinic acid (10 milligrams of platinum percc), and 21.3 cc of concentrated hydrochloric acid, the solution beingdiluted to 250 cc with water. The alumina particles were tumbled in thesolution for about 1/2 hour at room temperature utilizing a steamjacketed rotary dryer. Steam was thereafter applied to the dryer jacketand the solution evaporated to dryness in contact with the tumblingparticles. The particles were subsequently calcined in air for 1/2 hourat 390° F., and for an additional 1/2 hour at 975° C. The calcinedparticles were thereafter reduced in hydrogen for about 1 hour at 1050°F. to yield a catalyst comprising 0.22 wt. % platinum, and about 1.0 wt.% chloride. The average bulk density was approximately 0.84 grams percc.

EXAMPLE II

A portion of the catalyst produced by the method of Example I is placedin a continuous flow, fixed-bed isomerization plant of conventionaldesign. Substantially pure meta-xylene is used as the charge stock. Thecharge stock is commingled with about 8 moles of H₂ per mole ofhydrocarbon, heated to about 400° C., and continuously charged to thereactor containing the catalyst which is maintained at about a pressureof about 300 psig. Substantial conversion of meta-xylene to para-xyleneis obtained . . . i.e. greater than 80 percent of equilibrium.

EXAMPLE III

Another portion of the catalyst produced by Example I is used toisomerize ethylbenzene. The reactor is maintained at 300 psig. and 410°C. as ethylbenzene, commingled with 8 moles of H₂ per mole ofethylbenzene is continuously passed to the reactor at 2 LHSV.Substantial conversion of ethylbenzene to the three xylene isomers isobserved.

EXAMPLE IV

Another portion of the catalyst produced by Example I is used toisomerize ortho-xylene to para-xylene. The reactor is maintained at atemperature of 400° C., and a pressure of 300 psig. as ortho-xylene,commingled with 8 moles of H₂ per mole of ortho-xylene is passed to thereactor at a liquid hourly space velocity (LHSV) of 2.0 hr.⁻¹.Substantial conversion--i.e. greater than 80 percent of equilibriumconversion--of ortho-xylene to para-xylene is obtained.

EXAMPLE V

A catalyst identical to that produced in Example I but containing only0.40 wt. % combined chloride is used to isomerize 1-butene at a pressureof about 500 psig. and a temperature of about 140° C. in an appropriatecontinuous isomerization reactor. Substantial conversion to 2-butene isobtained.

EXAMPLE VI

Another portion of the catalyst utilized in Example V is charged to anappropriate continuous isomerization reactor maintained at a pressure ofabout 1000 psig. and a temperature of about 180° C. 3-methyl-1-butene iscontinuously passed to this reactor and a substantial conversion to2-methyl-2-butene is obtained.

EXAMPLE VII

Another catalyst identical to that produced in Example I, except thatthe catalyst particles are contacted with hydrogen fluoride to provide a2.7 weight percent combined fluoride content, is placed in anappropriate continuous isomerization reactor maintained at a pressure ofabout 300 psig. and a temperature of about 200° C. Normal hexane iscontinuously charged to the reactor and an analysis of the productstream shows substantial conversion to 2,2-dimethylbutane,2,3-dimethylbutane, 2-methylpentane, and 3-methylpentane.

EXAMPLE VIII

One hundred grams of the reduced catalyst composite of Example I areplaced in a glass-lined rotating autoclave along with 75 grams ofanhydrous aluminum chloride. The autoclave is sealed, pressured with 25psi of hydrogen and heated and rotated for 2 hours at 250° C. Theautoclave is allowed to cool, depressured through a caustic scrubber,opened and the final composite removed therefrom. Weighing of thiscomposite indicates a 15 wt. percent gain equivalent to the aluminumchloride sublimed and reacted thereon. The caustic scrubber is found tohave absorbed hydrogen chloride equivalent to about 5.0 wt. percent ofthe original composite corresponding to about 0.8 mole of HCl per moleof ACl₃ adsorbed.

EXAMPLE IX

A portion of the catalyst of Example VIII is used to isomerize normalbutane at a pressure of 300 psig., a 0.5 hydrogen to hydrocarbon moleratio, and a 1.0 LHSV at a temperature of 230° C. Substantial conversionof n-butane to isobutane is observed--approximately a conversion ofn-butane to isobutane of about 45 wt. % of the butane charge.

EXAMPLE X

Another portion of the catalyst of Example VII is placed in anappropriate continuous isomerization reactor maintained at a temperatureof about 210° C. and a pressure of about 250 psig. Methylcyclopentane iscontinuously passed to this reactor and a substantial conversion tocyclohexane is observed.

EXAMPLE XI

In this example, 4000 grams of a finely divided alpha-aluminamonohydrate (Catapal SB Alumina) was added to a rapidly stirred aqueousalkaline solution having a pH of about 7.5. The alumina contained about25 wt. % volatile matter, and the alkaline solution of 12.9 cc ofconcentrated ammonium hydroxide diluted to 3450 cc with water. Theresulting slurry was a stable suspension having a light creamyconsistency. The suspension was Newtonian in character and gave noindication of thixotropic or dilatant behavior. After about 30 minutesof continuous stirring, an aluminum nitrate solution was added, thesolution consisting of 595 grams of Al(NO₃)₃ 9 H₂ O dissolved in 1400 ccof water. The stirred suspension became very thin and extremely fluidfor about 10 seconds and thereafter set to thick paste with a solidscontent of about 33 wt. %. The paste was subsequently extruded, ovendried for about 12 hours at 110° C. and calcined for about 2 hours at650° C. in air containing about 3 wt. % steam. The dried and calcinedalumina product had a surface area of 217 m² /g, and a pore volume ofabout 0.35 cc/g in the 40-60 Angstrom diameter range.

About 250 cc of the alumina particles are immersed in 250 cc of animpregnating solution containing chloroplatinic acid, hydrogen chlorideand perrhenic acid in amounts sufficient to yield a final compositecontaining 0.60 wt. percent platinum, 0.2 wt. percent rhenium, and 0.85wt. percent combined chloride--all calculated on an elemental basis. Thealumina particles are tumbled in the solution for about 1/2 hour at roomtemperature utilizing a steam jacketed rotary dryer. Steam is thereafterapplied to the dryer jacket and the solution is evaporated to dryness incontact with the tumbling particles. The particles are subsequentlycalcined in air for 1/2 hour at 390° F., and for an additional 1/2 hourat 975° F. The calcined particles are thereafter reduced in hydrogen forabout 1 hour at 1050° F. to yield a finished catalyst.

EXAMPLE XII

A portion of the catalyst produced by the method of Example XI is placedin a continuous flow, fixed bed isomerization plant of conventionaldesign. Substantially pure metaxylene is used as the charge stock. Thecharge stock is commingled with about 8 moles of H₂ per mole ofhydrocarbon, heated to about 400° C. and continuously charged to thereactor containing the catalyst which is maintained at about a pressureof about 300 psig. Substantial conversion of meta-xylene to para-xyleneis obtained . . . i.e., greater than 80 percent of equilibrium.

EXAMPLE XIII

One hundred grams of the reduced catalytic composite of Example XI areplaced in a glass-lined rotating autoclave along with 75 grams ofanhydrous aluminum chloride. The autoclave is sealed, pressured to 25psig. with hydrogen and heated and rotated for 2 hours at 250° C. Theautoclave is allowed to cool, depressured through a caustic scrubber,opened and the final composite removed therefrom. Weighing of thiscomposite indicates a 15 weight percent gain equivalent to the aluminumchloride sublimed and reacted thereon.

EXAMPLE XIV

A portion of the catalyst of Example XIII is used to isomerize normalbutane at a pressure of 300 psig., a 0.5 hydrogen to hydrocarbon moleratio, and a 1 LHSV at a temperature of 230° C. Substantial conversionof n-butane to isobutane is observed--approximately a conversion ofn-butane to isobutane of about 45 weight percent of the butane charge.

EXAMPLE XV

About 250 cc of dried and calcined alumina particles from Example XI areimmersed in 250 cc of an impregnating solution containing chloroplatinicacid, hydrogen chloride and stannic chloride in amounts sufficient toyield a final composite containing 0.75 weight percent platinum and 0.5weight percent tin, calculated on an elemental basis. The impregnatedparticles are then dried at a temperature of about 300° F. for about anhour and thereafter calcined in an air atmosphere at a temperature ofabout 925° F. for about 1 hour. The resulting calcined spheres are thencontacted with an air stream containing H₂ O and HCl in a mole ratio ofabout 40:1 for about 4 hours at 975° F.

EXAMPLE XVI

A portion of the catalyst prepared in Example XV is placed, as acatalytic composite, in a continuous flow fixed bed isomerization plantof conventional design. The charge stock, containing on a weight percentbasis, 20% ethylbenzene, 10% para-xylene, 50% meta-xylene and 20%ortho-xylene is commingled with about 8 moles of hydrogen per mole ofhydrocarbon, heated to 400° C., and continuously charged at 4 hr.⁻¹liquid hourly space velocity (LHSV) to the reactor which is maintainedat a pressure of about 400 psig. and 400° C. The resulting productevidences essentially equilibrium conversion to para-xylene with onlyinsignificant amounts of cracked products thus indicating an efficientalkylaromatic isomerization catalyst.

EXAMPLE XVII

A portion of catalytic composite prepared in Example XV is placed in aglass-lined rotating autoclave along with anhydrous aluminum chloride.The autoclave is sealed, pressured to 25 psig. with hydrogen and heatedand rotated for 2 hours at 300° C. The autoclave is then allowed tocool, depressured through a caustic scrubber, opened and the finalcomposite removed therefrom. An analysis of this composite indicates a15 weight percent gain based on the original composite, equivalent tothe aluminum chloride sublimed and reacted thereon.

EXAMPLE XVIII

A portion of the catalyst prepared in Example XVII is placed in anappropriate continuous isomerization apparatus and used to isomerizenormal butane at a reactor pressure of 300 psig., a 0.5 hydrogen tohydrocarbon mole ratio, a 1 LHSV, and a reactor temperature of 230° C.Substantial conversion of normal butane to isobutane is observed.

We claim as our invention:
 1. A process for isomerizing an isomerizableparaffinic hydrocarbon which comprises contacting said paraffinichydrocarbon, at isomerization conditions, with a catalytic compositecomprising a combination of a platinum group metal component and analumina support wherein said support is prepared by admixing a finelydivided alpha-alumina monohydrate with an aqueous ammoniacal solutionhaving a pH of at least about 7.5 to form a stable suspension,commingling a catalytic metal salt of a strong acid with said suspensionto form the suspension into an extrudable paste or dough, extruding thepaste or dough to form an extrudate, drying and calcining said extrudateto form said alumina support.
 2. The process of claim 1 wherein saidcatalyst further comprises from about 0.01 to about 2 weight percentrhenium composited with said alumina.
 3. The process of claim 1 whereinsaid catalyst further comprises from about 0.01 to about 2 weightpercent germanium composited with said alumina.
 4. The process of claim1 wherein said catalyst further comprises from about 0.01 to about 5weight percent tin composited with said alumina.
 5. The process of claim1 wherein said platinum group metal is platinum.
 6. The process of claim1 wherein said alumina is a water hydrolysis product of an aluminumalkoxide.
 7. The process of claim 1 wherein said alumina is a waterhydrolysis product of an aluminum alkoxide produced by the Zieglerprocess.
 8. The process of claim 1 wherein said aqueous ammoniacalsolution has a pH from about 7.5 to about 8.5.
 9. The process of claim 1wherein said metal salt is an aluminum salt of a strong acid.
 10. Theprocess of claim 1 wherein said metal salt is aluminum nitrate.
 11. Theprocess of claim 1 wherein said metal salt is an aluminum salt of astrong acid employed in an amount to provide from about 2 to about 10weight percent of the alumina in the final product.
 12. The process ofclaim 1 wherein said suspension comprises from about 30 to about 60weight percent alumina.
 13. The process of claim 1 wherein said aluminais calcined at a temperature of from about 550° to about 750° C. toprovide a surface area from about 165 to about 215 m² /g, and a porevolume from about 0.3 to about 0.4 cc/g in a pore diameter range of fromabout 20 to about 80 Angstroms.
 14. The process of claim 1 wherein saidisomerization conditions include a temperature of about 0° C. to about425° C., a pressure of about atmospheric to about 100 atmospheres and aliquid hourly space velocity of about 0.1 to about
 20. 15. The processof claim 14 wherein said paraffinic hydrocarbon is commingled with about0.1 to about 10 moles of hydrogen per mole of hydrocarbon.
 16. Theprocess of claim 1 wherein said paraffinic hydrocarbon is a C₄ -C₉alkane.
 17. The process of claim 16 wherein said catalytic composite hascombined therewith about 1 to about 100 weight percent Friedel-Craftsmetal halide, calculated on a metal halide-free composite.